The migration from .Mac to MobileMe has gone very badly since its official launch on July 12.
First, there was widespread disenchantment that MobileMe's widely promoted "push" services actually don't push sync changes to desktop/notebook PCs. Customers weren't happy to learn that Macs have to poll the online service for data changes instead  which makes changes occur about every 15 minutes, not instantly.
Apple has documented this, saying "Selecting Automatic in Mac OS X allows your computer to immediately sync and update when there are any changes on the MobileMe servers. Those changes can come from your iPhone, iPod touch, the MobileMe website, or another computer. Changes made on your computer will be synced to the MobileMe "cloud" once every 15 minutes (or every hour in Mac OS X 10.4.11)."
Next, even those services still don't work reliably. Apple acknowledged this in an email to MobileMe subscribers that said,
We have recently completed the transition from .Mac to MobileMe. Unfortunately, it was a lot rockier than we had hoped.
Although core services such as Mail, iDisk, Sync, Back to My Mac, and Gallery went relatively smoothly, the new MobileMe web applications had lots of problems initially. Fortunately we have worked through those problems and the web apps are now up and running.
Another snag we have run into is our use of the word "push" in describing everything under the MobileMe umbrella. While all email, contact or calendar changes on the iPhone and the web apps are immediately synced to and from the MobileMe "cloud," changes made on a PC or Mac take up to 15 minutes to sync with the cloud and your other devices. So even though things are indeed instantly pushed to and from your iPhone and the web apps today, we are going to stop using the word "push" until it is near-instant on PCs and Macs, too.
We want to apologize to our loyal customers and express our appreciation for their patience by giving all current subscribers an automatic 30-day extension to their MobileMe subscription free of charge. Your extension will be reflected in your account settings within the next few weeks.
We hope you enjoy your new suite of web applications at me.com, in addition to keeping your iPhone and iPod touch wirelessly in sync with these new web applications and your Mac or PC.
You can read all the details about the 30-day extension to MobileMe here.
And now, it seem that many people who have their e-mail through Apple's online service can't get to the e-mail  and haven't been able to for several days. According to CNN Money, 1% of users can't get to mail. My recent check of Apple's MobileMe support site shows that "2% of MobileMe members cannot access MobileMe Mail. Service will be restored ASAP. We apologize for any inconvenience."
Not good! If you're considering subscribing to MobileMe, I urge you to hold off until Apple gets its act together.